Method and apparatus to eliminate fuel use for electric drive machines during trolley operation

ABSTRACT

A drive system for a machine having an engine, a generator, a trolley drive arrangement, a motor, wheels and auxiliary devices is provided. The drive system includes an inverter circuit and an auxiliary driver both being operatively connected to the trolley drive arrangement. The inverter circuit may be coupled to each of the generator and the motor. The auxiliary driver may be coupled to each of the generator and the auxiliary devices. The inverter circuit and the auxiliary driver may be configured to automatically communicate power from the trolley drive arrangement and any power from the auxiliary devices to the motor in a trolley propel mode, and automatically communicate power from the motor to the engine, the trolley drive arrangement, and optionally to a hybrid system if applicable, in a dynamic braking mode, while attached to trolley lines so as to eliminate fuel consumption while attached to the trolley lines.

TECHNICAL FIELD

The present disclosure relates generally to the operation of electricdrive machines, and more particularly, to systems and methods thateliminate fuel consumption during trolley operation and dynamic braking.

BACKGROUND

Electric drive systems for machines typically include a power circuitthat selectively activates at least one motor at a desired torque. Themotor is typically connected to a wheel or other traction device thatoperates to propel the machine. An electric drive system includes aprime mover, for example, an internal combustion engine that drives agenerator. The generator produces electrical power that is used to drivethe motor. When the machine is propelled, mechanical power produced bythe engine is converted to electrical power at the generator. Thiselectrical power is often processed and/or conditioned before beingsupplied to the motor. The motor transforms the electrical power backinto mechanical power to drive the wheels and propel the vehicle. Somemachines having an electrical drive system that utilizes an externalsource of power during certain modes of operation. Such a machine forexample may be an electric drive mining truck. When such a machine ispropelled fully loaded and connected to a trolley system, power is fedto the propel motors and converted to mechanical power to drive themachine.

The machine is retarded in a mode of operation during which the operatordesires to decelerate the machine. To retard the machine in this mode,the power from the engine is reduced. Typical machines may also includeservice brakes and other mechanisms for retarding to decelerate and/orstop the machine. As the machine decelerates, the momentum of themachine is transferred to the motor via rotation of the wheels. Themotor acts as a generator to convert the kinetic energy of the machineto electrical energy that is supplied to the drive system. Thiselectrical energy is typically dissipated (wasted) across an electricalgrid, stored in chargeable cells such as batteries or capacitors forlater use, or partially used to power auxiliary components such asblowers for cooling retarding grids.

Some machines, such as some hybrid machines, are configured to store theelectrical energy provided by the motor during a retarding mode ofoperation in energy storage devices or batteries for later use. Thestored energy is used to power auxiliary devices and/or drive motorsduring idling or propel modes of operation so as to minimize engineinvolvement and reduce fuel consumption. Although such storageconfigurations may reduce fuel consumption during retarding modes, theextra weight added to the vehicle may in fact increase fuel consumptionduring propel modes. Implementing storage configurations also introducessignificant cost and technological limitations, among other things.

A favored alternative to storage configurations serves to simply wastethe energy in the form of heat via a dynamic braking retarding grid ofresistors and insulators. To minimize overheating, a grid cooling systemhaving an electrically driven blower is often used to help dissipate theheat from the retarding grid. The blower motor is powered by the wasteenergy such that the engine is not required to cool the retarding grid.However, retarding grid configurations introduce several controllimitations. Among other things, these configurations prohibit operationof the grid cooling system without providing significant braking force.More specifically, because the grid cooling system is powered only bywaste energy that is supplied by the motor during retarding modes, thegrid cooling system is unable to operate once the machine exits theretarding mode without absorbing a prohibitively large amount of powerfrom the engine and consuming diesel fuel. These systems are susceptibleto temperature overshoot conditions, or conditions in which thetemperatures of the resistive elements and insulators of the retardinggrid sharply increase once a blower is shut off. Furthermore, inlow-power retarding modes, or when the retarding arrangement isoperating at less than nominal power, the shared DC bus of the drivesystem may collapse due to the comparatively large retardingrequirement. Additionally, these systems still require the engine to beoperated at lower RPMs and may reduce fuel consumption, but the engineis still needed to operate other auxiliary devices (i.e. parasiticloads).

Control systems which redirect the electrical energy generated frommotors during retarding or braking modes of operation, or regenerativeenergy, back into the engine are known to those skilled in the art as ameans to reduce fuel consumption and improve efficiency. Some existingcontrol systems include a drive system that feeds power generated bytraction motors during dynamic braking back into the main alternator torotate the engine. However, the retarding grids and the grid coolingmechanisms of such systems are linked to the same bus, and thus, cannotbe independently controlled. Furthermore, all of these systemsspecifically require switching of a transfer switch in order to redirectpower to the engine during dynamic braking modes.

Therefore, there is a need for a drive system and method that eliminatesfuel consumption during certain propel modes and during dynamic brakingmodes of operation. Specifically, there is a need for an electric drivesystem and method that automatically and more efficiently redirectspower generated at the fraction motor into the engine during dynamicbraking modes. There is also a need for an electric drive system andmethod which provides control of a grid cooling system that isindependent from control of the associated retarding grid.

SUMMARY OF THE DISCLOSURE

In one aspect of the present disclosure, a drive system is disclosed fora machine having an engine coupled to a generator, a motor operativelycoupled to drive wheels, and auxiliary devices. The drive systemincludes an inverter circuit coupled to each of the generator and themotor, and an auxiliary driver coupled to each of the generator and theauxiliary devices. A trolley drive arrangement is coupled to theinverter circuit and configured to automatically communicate externalpower to the motor and to the engine in a trolley propel mode, andautomatically communicate power from the motor to the engine and thetrolley drive arrangement in a dynamic braking mode so as to eliminatefuel consumption during the trolley propel and dynamic braking modes.

In another aspect of the disclosure, an electric drive machine isdisclosed. The electric drive machine includes an engine, a generatoroperatively coupled to the engine, a motor operatively coupled to one ormore drive wheels, an inverter circuit coupled to each of the generatorand the motor, a trolley drive arrangement, and an auxiliary drivercoupled to each of the generator and the auxiliary devices. The trolleydrive arrangement is coupled to the inverter circuit. The invertercircuit and the auxiliary driver are configured to automaticallycommunicate power from the trolley drive arrangement to the motor in apropel mode, and automatically communicate power from the motor to thegenerator in a dynamic braking mode. The auxiliary driver is configuredto transmit power to a DC bus during the trolley propel and dynamicbraking modes. The electric drive machine additionally includes aretarding grid coupled to the inverter circuit, and a grid coolingsystem coupled to the DC bus and configured to selectively cool theretarding grid. Control of the grid cooling system is independent fromcontrol of the retarding grid.

In yet another aspect of the disclosure, a method for eliminating fuelconsumption during trolley propel and dynamic braking of an electricdrive machine is disclosed. The machine includes at least an enginecoupled to a generator, a motor operatively coupled to drive wheels, andauxiliary devices. The method provides an inverter circuit in electricalcommunication between the generator and the motor as well as anauxiliary driver in electro-mechanical communication between thegenerator and the auxiliary devices. The method further determines acurrent mode of operation of the electric drive machine, automaticallydirects electrical power from the trolley drive arrangement to the motorin a trolley propel mode through at least one of the inverter circuitand the auxiliary driver if the current mode of operation is in trolleypropel mode, and automatically directs electro-mechanical power from themotor a to a one of the engine and the trolley drive arrangement in adynamic braking mode through at least one of the inverter circuit andthe auxiliary driver if the current mode of operation is in a dynamicbraking mode.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a general schematic view of an exemplary drive system asapplied to an electric drive machine;

FIG. 2 is a detailed schematic view of another exemplary drive system;

FIG. 3 is a detailed schematic view of another exemplary drive system;

FIG. 4 is a detailed schematic view of another exemplary drive system;

FIG. 5 is a detailed schematic view of another exemplary drive system;

FIG. 6 is a schematic view of an exemplary controller for an electricdrive system;

FIG. 7 is a flow diagram of an exemplary method for eliminating fuelconsumption in an electric drive machine during trolley application;

FIG. 8 is a diagrammatic view of an electric drive machine in a propelmode during trolley operation;

FIG. 9 is a diagrammatic view of an electric drive machine in a dynamicbraking mode during trolley operation; and

FIG. 10 is a diagrammatic view of an electric drive machine in an idlingmode of operation.

DETAILED DESCRIPTION

Referring to FIG. 1 schematically illustrates an exemplary drive system100 as applied to a machine 102, such as for example an electric driveoff-road truck. The machine 102 typically includes a prime mover 103such as an internal combustion engine 104, a generator 106, powerelectronics 107, one or more motors 108, one or more wheels 110, aretarding grid 112, a grid cooling system 114 and one or more auxiliarydevices 116. In this example, drive system 100 also involves a trolleydrive arrangement 109 such as a trolley lines 111 which includes twooverhead lines as is recognized in the industry but are not shown. Itshould be noted here that the trolley lines 111 may be provided topropel the machine in an up hill direction, or a down hill directiondepending on where the load and dump locations are positioned. Thetrolley drive arrangement 109 also includes a pantograph(s) 113positioned on the machine to connect to the trolley lines 111, and atrolley cabinet 115 interfaces the pantograph(s) 113 with the powerelectronics 107. As shown, power electronics 107 is provided with atleast an inverter circuit 118 and an auxiliary driver 120. The invertercircuit 118 may include one or more rectifiers 122, inverters 124, orany combination thereof, and be disposed between the generator 106 andthe motor 108. The auxiliary driver 120 may be disposed between thegenerator 106 and the auxiliary devices 116 and include an auxiliarygenerator, winding assembly, DC motor, or any other means for allowingbidirectional electrical communication therebetween.

During a standard propel mode of operation, or when the machine 102 isbeing accelerated, power may be transferred from the engine 104 andtoward the wheels 110, as indicated by solid arrows, to cause movement.Specifically, the engine 104 may produce an output torque to thegenerator 106, which in turn converts the mechanical torque intoelectrical power. The electrical power may be generated in the form ofalternating current (AC) power. The AC power may then be converted todirect current (DC) and converted again to the appropriate amount of ACpower by the inverter circuit 118. The resulting AC power may then beused to drive the one or more motors 108 and the wheels 110, as is wellknown in the art. Also, during the propel mode, the auxiliary driver 120may communicate any power supplied by the generator 106 to one or moreauxiliary devices 116, and/or communicate any power supplied by one ormore auxiliary devices 116 to the generator 106 so as to at leastpartially drive the engine 104 and the motors 108 as described above.

Alternatively, during a trolley propel mode of operation when themachine 102 is being accelerated, power may be transferred from thetrolley lines 111 to the power electronics 107 toward the wheels 110, asindicated by dark solid arrows, to cause movement. Specifically,electrical power from the trolley lines 111 in the form of directcurrent (DC) is converted to the appropriate amount of AC power by theinverter 124. The resulting AC power is then be used to drive the one ormore motors 108 and the wheels 110, as was described above. Also, duringthe propel mode, power supplied from the trolley lines 111 back drivingthe generator 106 thus supplying power to the auxiliary driver 120 toone or more auxiliary devices 116, and/or communicate any power suppliedby one or more auxiliary devices 116 to the generator 106 so as to atleast partially drive the engine 104 and the motors 108 as describedabove. Power from one or more auxiliary devices 116 may also be providedback to the trolley lines 111.

During a dynamic braking mode of operation, or when the motion of themachine 102 is to be retarded, power may be generated by the mechanicalrotation at the wheels 110 and directed toward the retarding grid 112,as indicated by dashed arrows and/or back to the trolley lines 111. Inparticular, the kinetic energy of the machine 102 may be converted intorotational power at the wheels 110. Rotation of the wheels 110 mayfurther rotate the motor 108 so as to generate electrical power, forexample, in the form of AC power. The inverter circuit 118 may serve asa bridge to convert the power supplied by the motor 108 into DC power.Dissipation of the DC power generated by the motor 108 may produce acounter-rotational torque at the wheels 110 to decelerate the machine102. Such dissipation may be accomplished by passing the generatedcurrent provided by the inverter circuit 118 through a resistance, suchas the retarding grid 112 shown and may also supply power back to thetrolley lines 111. Excess electricity may be communicated, by thetrolley lines 111, back to a central charge unit at an electricalsubstation (not shown) or transformed into heat generated at theretarding grid 112 and be expelled using the grid cooling system 114.Power to the grid cooling system 114 may be supplied by the generator106 or the trolley lines 111 via a communication path through theauxiliary driver 120. Similarly, the auxiliary driver 120 may supplypower provided by the generator 106 or the trolley lines 111 to any oneor more of the auxiliary devices 116 available on the machine 102.

Referring now to FIG. 2, a more detailed schematic of an example of thedrive system 100 as applied to machine 102 is provided. As in theexample of FIG. 1, the machine 102 of FIG. 2 also includes prime mover103, such as the engine 104, which serves as the machine's primarysource of power. The engine 104 may be configured to provide direct orindirect power to parasitic loads 126 via belts, hydraulic systems, andthe like. The engine 104 may be mechanically coupled to generator 106through a coupling 128. The machine 102 has one or more motors 108mechanically coupled to one or more wheels 110 via another coupling 128.Machine 102 also includes a retarding grid 112, a grid cooling system114 and auxiliary devices 116 may also be provided. The auxiliarydevices 116 may include, for example, a heating, ventilation and airconditioning (HVAC) system 130, a hybrid system 132 having an energystorage device 134 and conditioning circuitry 136, a battery chargingdevice 138, or any electrically driven pump or accessory 140.

As shown in FIG. 2, the drive system 100 may provide the machine 102with at least an inverter circuit 118 to provide electricalcommunication between the generator 106 and/or the trolley lines 111 tothe motor 108. The inverter circuit 118 may include a configuration ofone or more rectifiers 122 and inverters 124 as shown in FIG. 1. In analternative example, the inverter circuit 118 provides a parallelconfiguration of inverters 124 and/or a bidirectional inverter 142 inplace of, for example, the rectifier 122 of FIG. 1, so as to enablebidirectional communication of electrical power between the generator106 and/or the trolley lines 111 to the motor 108. The inverter circuit118 may additionally be electrically coupled to the retarding grid 112so as to dissipate any excess energy therethrough and/or send a portionof the electrical power back to the trolley lines 111. Alternatively,any one or more of the auxiliary devices 116, such as the hybrid system132, may also direct any energy generated therefrom toward the auxiliarydriver 120 and/or the generator 106.

Still referring to FIG. 2, the drive system 100 may further provide themachine 102 with an auxiliary driver 120 to provide electricalcommunication between the generator 106 and the auxiliary devices 116.More specifically, the auxiliary driver 120 may include a windingassembly 144 or a series of tapped windings electrically coupled to thegenerator 106 so as to transform AC power supplied by the generator 106to an appropriate amount of AC power as needed by the auxiliary devices116. The auxiliary driver 120 may also provide a parallel configurationof inverters 124 or a bidirectional inverter 142 to convert AC powerfrom the generator 106 to the appropriate DC power necessary for drivingthe auxiliary devices 116. Additionally, when in trolley propel mode DCpower from the trolley lines 111 is converted by bidirectional inverter142 to AC power to operate the generator 106 as a motor and windingassembly 144 as to transform AC power supplied by the trolley lines 111to an appropriate amount of AC power as needed by the auxiliary devices116. As described before, the auxiliary driver 120 may use the convertedAC power from the trolley lines 111 to the appropriate DC powernecessary for driving the auxiliary devices 116. The DC power providedby the bidirectional inverter 142 may be supplied in parallel to each ofthe auxiliary devices 116 via a DC bus 146, link, or the like.Similarly, DC power provided by the auxiliary devices 116 may betransmitted to the auxiliary driver 120 via the DC bus 146, convertedinto AC power via the bidirectional inverter 142, and supplied to thegenerator 106 via the winding assembly 144. This AC power may also beconverted by the bidirectional inverter 142, and supplied back to thetrolley lines 111 for storage at a central charge unit at an electricalsubstation (not shown). The auxiliary driver 120 may also be configuredto selectively control power to an inverter 124 and/or a blower motor148 of the grid cooling system 114 via the DC bus 146 in a manner thatis independent from control of the retarding grid 112. As power to thegrid cooling system 114 via the DC bus 146 is supplied independentlyfrom power to the retarding grid 112, the grid cooling system 114 may beenabled when predetermined temperature thresholds of the retarding grid112 are exceeded regardless of the operating mode of the machine 102.

Turning to FIG. 3, an exemplary schematic of another drive system 100 asapplied to machine 102 is provided. As in previous examples, machine102, of FIG. 3, may include engine 104 configured to provide power toparasitic loads 126 via belts, hydraulic systems, and the like. Theengine 104 may also be mechanically coupled to generator 106 throughcoupling 128, or the like. Movement of the machine 102 may be providedby one or more motors 108 that are mechanically coupled to one or morewheels 110 via a coupling 128. The machine 102 may additionally providea retarding grid 112 and a grid cooling system 114 having an inverter124 and a blower motor 148 for actively cooling the retarding grid 112.In addition to the grid cooling system 114, auxiliary devices 116 mayinclude a heating, ventilation and air conditioning (HVAC) system 130, ahybrid system 132 having an energy storage device 134 and conditioningcircuitry 136, a battery charging device 138, or any other electricallydriven pump or accessory 140.

As in the example of FIG. 2, the drive system 100 of FIG. 3 may providethe machine 102 with at least an inverter circuit 118 to provideelectrical communication between the generator 106 and/or the trolleylines 111 to the motor 108. The inverter circuit 118 may provide aparallel configuration of inverters 124 and/or a bidirectional inverter142 in place of, for example, the rectifier 122 of FIG. 1, so as toenable bidirectional communication of electrical power between thegenerator 106 and/or the trolley lines 111 to the motor 108. Theinverter circuit 118 may additionally be electrically coupled to theretarding grid 112 and configured to dissipate any excess energytherethrough and/or send a portion of the electrical power back to thetrolley lines 111. Alternatively, any one or more of the auxiliarydevices 116, such as the hybrid system 132, may also direct any energygenerated therefrom toward the auxiliary generator 150.

The drive system 100 may also provide an auxiliary driver 120 to provideelectrical communication between the generator 106 or the trolley lines111 and the auxiliary devices 116. In contrast to the winding assembly144 of FIG. 2, the auxiliary driver 120 may include an auxiliarygenerator 150 that is mechanically coupled to the main or generator 106as shown. Similar to the winding assembly 144, the auxiliary generator150 may serve to convert any AC power supplied by the generator 106 toan appropriate amount of AC power as needed by, for example, theauxiliary devices 116. Similarly DC power from the trolley lines 111 maybe converted to AC power by the bidirectional inverter 142 may drive thegenerator 106 acting as a motor to drive the auxiliary generator 150 toan appropriate amount of AC power as needed by the auxiliary devices116. A parallel configuration of inverters 124 or a bidirectionalinverter 142 may also be provided to convert any AC power from theauxiliary generator 150 to the appropriate DC power necessary fordriving the auxiliary devices 116. The DC power provided by thebidirectional inverter may be supplied in parallel to each of theauxiliary devices 116 via DC bus 146, link, or the like. Similarly, anyDC power provided by the auxiliary devices 116 may be transmitted to theauxiliary driver 120 via the DC bus 146, converted into AC power via thebidirectional inverter 142 and supplied to the generator 106 via theauxiliary generator 150. This AC power may also be converted by thebidirectional inverter 142, and supplied back to the trolley lines 111for storage at a central charge unit at an electrical substation (notshown). The auxiliary driver 120 may also be configured to selectivelycontrol power to the grid cooling system 114 via the DC bus 146 in amanner that is independent from control of the retarding grid 112.

In alternative examples drive system 100 may be modified and fitted ontomachines 102 with pre-existing electric drive configurations, as shownfor example in FIG. 4. As in previous examples, the machine 102 of FIG.4 includes engine 104 configured to supply power to parasitic loads 126via belts, hydraulic systems, and the like, as well as to generator 106via a mechanical coupling 128, or the like. The machine 102 may furtherinclude one or more motors 108 for driving one or more wheels 110 via amechanical coupling 128. Additionally, the machine 102 may support aretarding grid 112 and a grid cooling system 114 having an inverter 124and a blower motor 148 for actively cooling the retarding grid 112. Inaddition to the grid cooling system 114, the auxiliary devices 116 mayinclude a heating, ventilation and air conditioning (HVAC) system 130, ahybrid system 132 having an energy storage device 134 and conditioningcircuitry 136, a battery charging device 138, or any other electricallydriven pump or accessory 140.

In contrast to the examples of FIGS. 2 and 3, the drive system 100 ofFIG. 4 may correspond to a pre-existing inverter configuration, or theinverter circuit 118 shown. Moreover, the inverter circuit 118 mayinclude at least one rectifier 122 and an inverter 124, both of whichare configured to transmit power unidirectionally from the generator 106and/or the trolley lines 111 toward the motor 108. The inverter circuit118 may additionally be electrically coupled to the retarding grid 112and configured to dissipate any excess energy therethrough.

As the inverter circuit 118 of FIG. 4 prohibits the return of anyelectrical energy that is generated by the motor 108 during dynamicbraking or retarding modes, the auxiliary driver 120 may be configuredto redirect any such energy back to the engine 104 as shown.Specifically, in addition to an auxiliary generator 150 that ismechanically coupled to the engine 104 and/or the generator 106, theauxiliary driver 120 may further include a motor generator 152 that ismechanically coupled to the motor 108, the wheels 110 and/or any othermeans for causing motion. The motor generator 152 may be configured totransmit any mechanical energy that is supplied by the motor 108 and/orthe wheels 110 during dynamic braking and/or trolley mode of operationthrough an inverter 124 to be converted into DC power. The convertedelectrical energy may be passed through a DC bus 146 and thentransmitted to a second inverter 124 that is coupled to the auxiliarygenerator 150. The auxiliary generator 150 may convert the receivedelectrical energy into mechanical energy used to drive the engine 104during dynamic braking and trolley modes. The DC bus 146 may also beconfigured to supply converted DC power to any one or more of theauxiliary devices 116 including the grid cooling system 114. As inprevious examples, the drive system 100 may enable selective control ofthe grid cooling system 114 that is independent from control of theretarding grid 112. Alternatively, any one or more of the auxiliarydevices 116, such as the hybrid system 132, may also communicate anyenergy generated therefrom toward the auxiliary generator 150.

In a similar example drive system 100 may be modified and fitted ontomachines 102 with pre-existing electric drive configurations, as shownfor example in FIG. 5. As in previous examples, the machine 102 of FIG.5 includes engine 104 configured to supply power to parasitic loads 126via belts, hydraulic systems, and the like, as well as to generator 106via a mechanical coupling 128, or the like. The machine 102 may furtherinclude one or more motors 108 for driving one or more wheels 110 via amechanical coupling 128. Additionally, the machine 102 may support aretarding grid 112 and a grid cooling system 114 having an inverter 124and a blower motor 148 for actively cooling the retarding grid 112. Inaddition to the grid cooling system 114, the auxiliary devices 116 mayinclude a heating, ventilation and air conditioning (HVAC) system 130, ahybrid system 132 having an energy storage device 134 and conditioningcircuitry 136, a battery charging device 138, or any other electricallydriven pump or accessory 140.

In contrast to the examples of FIGS. 2 and 3, the drive system 100 ofFIG. 5 may correspond to a pre-existing inverter configuration, or theinverter circuit 118 shown. Moreover, the inverter circuit 118 mayinclude at least one rectifier 122 and an inverter 124, both of whichare configured to transmit power unidirectionally from the generator 106and/or the trolley lines 111 toward the motor 108. The inverter circuit118 may additionally be electrically coupled to the retarding grid 112and configured to dissipate any excess energy therethrough.

As the inverter circuit 118 of FIG. 5 prohibits the return of anyelectrical energy that is generated by the motor 108 during dynamicbraking or retarding mode, the auxiliary driver 120 may be configured toredirect any such energy back to the engine 104 as shown. Specifically,in addition to a DC motor 154 that is mechanically coupled to the engine104 and/or the generator 106, the auxiliary driver 120 may furtherinclude a DC/DC converter such as a step down chopper 156 that iselectrically coupled to the inverter circuit 118. The DC/DC converter156 may be configured to transmit any electrical energy that is suppliedby the trolley drive arrangement 109 during dynamic braking or retardingmode to the auxiliary devices 116 during trolley mode of operation. Theelectrical energy may be passed through DC bus 146 and then transmittedto through a contactor 158 and supplied to DC motor 154. The DC motor154 is connected to the generator 106 by coupling 128 and used to drivethe engine 104 during dynamic braking and trolley modes. The DC bus 146may also be configured to supply DC power to any one or more of theauxiliary devices 116 including the grid cooling system 114. As inprevious examples, the drive system 100 may enable selective control ofthe grid cooling system 114 that is independent from control of theretarding grid 112. Alternatively, any one or more of the auxiliarydevices 116, such as the hybrid system 132, may also communicate anyenergy generated therefrom toward the DC motor 154 to the generator 106.

Overall control of the drive system 100 as well as the machine 102 maybe managed by a controller 200 of the machine 102, as shown in FIG. 6.The controller 200 may take the form of one or more processors,microprocessors, microcontrollers, electronic control modules (ECMs),electronic control units (ECUs), or any other suitable means forelectronically controlling functionality of the drive system 100 and/ormachine 102. The controller 200 may be configured to operate accordingto a predetermined algorithm or set of instructions for controlling thedrive system 100 based on the various operating conditions of themachine 102. Such an algorithm or set of instructions may be read intoan on-board memory of the controller 200, or preprogrammed onto astorage medium or memory accessible by the controller 200, for example,in the form of a floppy disk, a hard disk, optical medium, random accessmemory (RAM), read-only memory (ROM), or any other suitablecomputer-readable storage medium commonly used in the art.

As shown in FIG. 6, the controller 200 may be in electricalcommunication with the engine 104, the generator 106, the invertercircuit 118, the auxiliary driver 120, the trolley drive arrangement109, the retarding grid 112, the grid cooling system 114, and the like.The controller 200 may also be coupled to various other components,systems or subsystems of the machine 102. By way of such connections,the controller 200 may receive data pertaining to the current operatingparameters of the drive system 100 and the machine 102 as input signals.The input signals may be provided by, for example, a plurality ofsensors associated with each component. In response to such input, thecontroller 200 may perform the necessary determinations and transmit anyoutput signals corresponding to the actions that need to be performed.The output signals may be integrated commands that are transmitted tovarious actuators or electronic devices, such as transistors oractuators, which are associated with the relevant components. Thecontroller 200 may also be electrically coupled to any other componentor device of the machine 102 that may be related to the inverter circuit118, auxiliary driver 120, trolley drive arrangement 109, retarding grid112, grid cooling system 114, and the like.

During operation of the machine 102, the controller 200 may receive aretarding command from an input node 202. The retarding command providedat the input node 202 may be generated in response to displacement of amanual control by the operator of the machine 102. The retarding commandmay alternatively be a command signal generated by the controller 200,or another controller of the machine that monitors or governs the speedof the machine 102, for example, a speed governor or a speed limiter.The controller 200 may receive and interpret the retarding commandaccording to a control system or algorithm operating therein. Thecontrol system may determine a magnitude of the retarding beingcommanded, for example, in units of energy or power. Based on such data,the controller 200 may determine the degree of energy to be dissipatedand respond accordingly. In examples having two retarding grids 112, forexample, the controller 200 may determine whether first, second, or bothretarding grids 112 should provide a contribution to retarding energydissipation. Alternatively, a portion of the retarding energy may bedirected back to the trolley lines 111 to aid in the energy dissipation.This determination or calculation may be based on various machineoperating parameters. The parameters may include the current speed, thepayload, the rate of acceleration, the desired speed, the inclination,the rate of change of the command to retard the machine 102, and thelike, which may be input to the controller 200 via one or moreadditional input nodes 204.

FIG. 7 diagrammatically illustrates an exemplary method by which such acontroller 200 may operate the drive system 100. In an initial step, thecontroller 200 may determine the current mode of operation of themachine 102. For example, based on the input signals at nodes 202, 204,the controller 200 may determine if the machine 102 is in a propel mode,dynamic braking or retarding mode, an idling mode, trolley mode, or anyother operating mode available on the machine 102. Based on the inputsignals at nodes 202, 204, the controller 200 may further determine ifthere is to be a change in the operating mode. Specifically, thecontroller 200 may determine the current and/or next operating modebased on, for example, the current speed, the payload, the rate ofacceleration, the inclination of the machine, the desired speed, therate of change of the command to retard the machine 102, and the like.In a propel mode, the drive system 100 may be configured to at leastautomatically direct power from the generator 106 or the trolley drivearrangement 109, as well as any power supplied by the auxiliary devices116, to the motor 108 to drive the wheels 110. Moreover, the drivesystem 100 may allow any communication of power from the generator 106or trolley drive arrangement 109 to the auxiliary devices 116, and ifapplicable, from the auxiliary devices 116 to the generator 106 or backto the trolley lines 111. In a trolley attached mode, the drive system100 may be configured to at least automatically direct power from thetrolley drive arrangement 109, as well as any power supplied by theauxiliary devices 116, to the motor 108 to drive the wheels 110 and tothe generator 106 to at least partially drive the engine 104 and allowthe engine 104 to be powered off, or stop fuel supply to the engine 104.In a dynamic braking or retarding mode, the drive system 100 may beconfigured to at least automatically direct power generated by the motor108 to the generator 106 or trolley lines 111 to at least partiallydrive the engine 104 and allow the engine 104 to be powered off, or stopfuel supply to the engine 104, or direct a portion of the energy back tothe trolley lines 111 through the trolley drive arrangement 109 forstorage a central substation (not shown). The drive system 100 mayfurther direct power from the generator 106 to the auxiliary devices116. In an optional idling mode, the drive system 100 may automaticallyallow any intercommunication of power between the generator 106 and theauxiliary devices 116. During such an idling mode, the hybrid system 132may store enough charge to allow the engine 104 to be powered off, orstop fuel injection, and further, allow the auxiliary devices 116 tooperate without any power from the generator 106 or trolley drivearrangement 109. In such a way, the auxiliary devices 116 may provideenough power to spin the engine 104 and drive the parasitic loads 126 ofthe engine 104, rapidly spin up the engine 104 when shifting into apropel mode, or even start the engine 104 from a stand still, allwithout any consumption of fuel.

FIG. 8 diagrammatically illustrates the machine 102 operating in atrolley propel mode. The trolley propel mode may be desired if thecombination of parameters provided to the controller 200 indicates, forexample, that a desired speed is greater than a current detected speedand/or that the machine 102 is to be accelerated or is beginning a climbor starting to descend on a mine haul road and that connection to thetrolley lines 111 is actuated. During the trolley propel mode, thetrolley drive arrangement 109 may serve as the primary source of powerof drive and allow the engine 104 to power down and stop the consumptionof fuel. Electrical energy from the trolley lines 111 is directed by thepantographs 113 to the trolley cabinet 115 and then be automaticallypassed through the inverter circuit 118 to drive the one or more motors108 and wheels 110. During the trolley propel mode, the auxiliary driver120 allows bidirectional communication between the generator 106 and theauxiliary devices 116. For instance, the electrical energy from thetrolley lines 111 may be passed through the auxiliary driver 120 to beconverted into DC power and transmitted to a DC bus 146 shared by theauxiliary devices 116. The electrical energy from the trolley lines 111may also be directed to the generator 106 and acting as a motor used toturn the engine so as to operate the auxiliary devices 116 such as bybelts, couplings or other connection. Alternatively, energy generated byany alternate energy source, such as the hybrid system 132, may supplypower through the DC bus 146 and the generator 106 to assist the engine104 or to be sent back to the trolley lines 111 for storage.Accordingly, the direction of power flow through the auxiliary driver120 may depend on the instantaneous needs and/or capabilities of thedrive system 100. The retarding grid 112 and the grid cooling system 114may be disabled during the propel mode but may continue to operate thegrid cooling system 114 to prevent over shoot.

FIG. 9 diagrammatically illustrates the machine 102 operating in adynamic braking or retarding mode. The dynamic braking mode may bedesired if the combination of parameters provided to the controller 200indicates, for example, that the desired speed is less than a currentdetected speed and/or that the machine 102 is to be decelerated. Duringthe dynamic braking mode, the one or more wheels 110 and motors 108 mayserve as the primary power source. Moreover, rotation of the wheels 110may turn the one or more motors 108 and cause the motors 108 to supplyelectrical energy in the form of, for example, AC power. As the invertercircuit 118 is bidirectional, the inverter circuit 118 may receive theelectrical energy provided by the motors 108 and convert the AC powerinto DC. The DC power may then be sent back to the trolley lines 111 oradjusted and converted back into AC power, and supplied to the generator106. The inverter circuit 118 may further apply the DC power to theretarding grid 112, or the chopper and/or contactor circuits 154, to beused by the auxiliary devices 116, or snet to the retarding grid 112, tobe dissipated in the form of heat. The power supplied to the generator106 may be used to mechanically drive the engine 104 temporarilyeliminate the use of fuel during the dynamic braking mode of operation.The power supplied to the generator 106 may further be used to supplyenergy to the auxiliary devices 116 via the auxiliary driver 120. Inparticular, the auxiliary driver 120 may convert the AC power providedto the generator 106, the DC motor 154 or additional windings 144 intoDC power to be passed along to the DC bus 146. The DC power may be usedto power the auxiliary devices 116 attached to the DC bus 146. Amongother things, the DC power may be used to supply power to the gridcooling system 114, or blower inverter and blower motor 148, so as tocool the retarding grid 112. In such a way, power to the grid coolingsystem 114 may be controlled independently from the retarding grid 112.This allows the grid cooling feature to be accessible during any otheroperating mode as needed via the auxiliary driver 120. As control of thegrid cooling system 114 is not limited to the retarding mode, theretarding grid 112 may be cooled even after exiting the retarding modeso as to minimize, for instance, temperature overshoot conditionscommonly associated with the resistive elements and/or insulators ofretarding grids 112.

In a further modification, the machine 102 may operate in an optionalidling mode as diagrammatically shown in FIG. 10. The idling mode may bedesired if the combination of parameters provided to the controller 200indicates, for example, that the desired and current speeds are nulland/or that there is no desired acceleration or deceleration. During theidling mode, the engine 104 may be supplied with enough fuel to maintainthe idle. Optionally, once the energy storage device 134 is fullycharged, the controller 200 may automatically enable engine shutoff toconserve fuel while power supplied by the energy storage device 134 maybe used to maintain the idle. As there is no movement in the wheels 110during the idling mode, the inverter circuit 118 and the retarding grids112 may be temporarily disabled. In the machine 102 having a hybridsystem 132 installed thereon, power may be initially supplied by theenergy storage device 134 to operate, for example, battery chargingdevices 138 as well as electric pumps and accessories 140. If the chargeof the energy storage device 134 reaches a preset minimum threshold, thecontroller 200 may enable the inverter 124 of the auxiliary driver 120to supply power to the generator 106 and invoke the engine 104 to start.While the engine 104 is idling, the inverter 124 of the auxiliary driver120 may begin drawing power from the generator 106 or use the trolleydrive arrangement to power the generator 106 to operate the electricpumps and accessories 140 and also to recharge the energy storage device134.

INDUSTRIAL APPLICABILITY

Exemplary off-highway trucks are commonly used in mines, constructionsites and quarries. The off-highway trucks may have payload capabilitiesof 100 tons or more and travel at speeds of 40 miles per hour or morewhen fully loaded.

Such work trucks or machines must be able to negotiate steep inclinesand operate in a variety of different environments. In such conditions,these machines frequently enter into a trolley propel mode and a dynamicbraking or retarding mode of operation for extended periods of time. Itis a shared interest to minimize or eliminate the amount of fuelconsumed during such Trolley propel and dynamic braking modes and makeefficient use of the power generated by the traction motors withoutadversely affecting overall machine performance. The systems and methodsdisclosed herein allow the drive systems of electric drive machines tocompletely eliminate fuel consumption during trolley propel and dynamicbraking modes while supplying regenerative power to machine subsystemsand accessories. The disclosed systems and methods further allowindependent control of at least a grid cooling system so as to minimizeoverheating of the retarding grid regardless of the mode of operation.

From the foregoing, it will be appreciated that while only certainexamples have been set forth for the purposes of illustration,alternatives and modifications will be apparent from the abovedescription to those skilled in the art. These and other alternativesare considered equivalents and within the spirit and scope of thisdisclosure and the appended claims.

What is claimed is:
 1. A drive system for a machine having an enginecoupled to a generator, a motor operatively coupled to drive wheels, andauxiliary devices, the drive system comprising: an inverter circuitcoupled to each of the generator and the motor; a trolley drivearrangement coupled to the inverter circuit and configured toautomatically communicate external power to the motor and to thegenerator in a trolley propel mode and to automatically communicatepower from the motor to the generator and the trolley drive arrangementin a dynamic braking mode, thereby back driving the engine and allowingthe supply of fuel to be shut off during the trolley propel and dynamicbraking modes.
 2. The drive system for the machine in claim 1 includingan auxiliary driver coupled to each of the generator and the auxiliarydevices, the inverter circuit and the auxiliary driver configured toautomatically communicate power from the trolley drive arrangement andany power from the auxiliary devices to the motor in a propel mode, andautomatically communicate power from the motor to the generator and thetrolley in a dynamic braking mode so as to eliminate fuel consumptionduring the dynamic braking and mode trolley mode.
 3. The drive system ofclaim 2, wherein the auxiliary driver includes at least one of anauxiliary generator and a winding assembly coupled to the generator andelectrically coupled to the auxiliary devices.
 4. The drive system ofclaim 3, wherein the auxiliary driver includes a bidirectional inverterenabling bidirectional electrical communication between the generatorand the auxiliary devices.
 5. The drive system of claim 3, wherein theinverter circuit includes one or more of an inverter and a rectifierconfigured to automatically communicate electrical power from thegenerator to the motor so as to at least partially drive the drivewheels during the propel mode, and automatically configured tocommunicate electrical power from the motor to the generator so as totransmit power to the engine during the trolley mode.
 6. The drivesystem of claim 3, wherein the inverter circuit includes a bidirectionalinverter configured to automatically communicate electrical power fromthe generator to the motor so as to at least partially drive the drivewheels during the propel mode, and automatically communicate electricalpower from the motor to the generator so as to transmit power to theengine during the dynamic braking mode.
 7. The drive system of claim 3,wherein the auxiliary driver is configured to at least partiallycommunicate power from the motor to the auxiliary devices during thedynamic braking mode.
 8. The drive system of claim 3, wherein theauxiliary driver includes a motor generator mechanically coupled to themotor and an auxiliary generator mechanically coupled to the engine, themotor generator and the auxiliary generator configured to communicatepower from the motor to the engine during the dynamic braking mode. 9.The drive system for the machine in claim 1 including an auxiliarydriver coupled to each of the generator and the auxiliary devices, theinverter circuit and the auxiliary driver configured to automaticallycommunicate power from the trolley drive arrangement to power anyauxiliary devices and the motor in a propel mode, and automaticallycommunicate power from the trolley to the auxiliary devices and thegenerator in a dynamic braking mode so as to eliminate fuel consumptionduring the dynamic braking mode and trolley mode.
 10. The drive systemof claim 9, wherein the auxiliary driver includes at least one a DCmotor electrically coupled to the auxiliary devices.
 11. The drivesystem of claim 10, wherein the auxiliary driver transmits electricalpower to a DC bus during the trolley mode, the auxiliary devices areconfigured to draw electrical power from the DC bus during the dynamicbraking mode.
 12. The drive system of claim 10, wherein the auxiliarydriver includes a DC/DC converter enabling electrical communicationbetween the trolley drive arrangement and the DC bus and power the DCmotor through a contactor from the DC bus to power the generator. 13.The drive system of claim 10, wherein the auxiliary driver includes arectifier enabling unidirectional electrical communication between theDC motor and the auxiliary devices.
 14. The drive system of claim 1,wherein the inverter circuit is electrically coupled to a retarding gridand the auxiliary driver is in electrical communication with a gridcooling system, control of the grid cooling system being independentfrom control of the retarding grid.
 15. An electric drive machine,comprising: an engine; a generator operatively coupled to the engine; amotor operatively coupled to one or more drive wheels; a invertercircuit coupled to each of the generator and the motor; a trolley drivearrangement coupled to the inverter circuit; an auxiliary DC busconnected to a plurality of auxiliary devices; an auxiliary driverconnected to each of the generator and the auxiliary devices, theauxiliary driver configured to transmit power to the auxiliary DC busduring a trolley propel mode and a dynamic braking mode; a one of theinverter circuit and the auxiliary driver configured to automaticallycommunicate power from the trolley drive arrangement to the motor andthe auxiliary devices in the trolley propel mode, and automaticallycommunicate power from the motor to the generator and the trolley drivearrangement in a dynamic braking mode, thereby back driving the engineand allowing the supply of fuel to be shut off during the trolley propeland dynamic braking modes; a retarding grid coupled to the invertercircuit; and a grid cooling system coupled to the auxiliary DC bus andconfigured to selectively cool the retarding grid, control of the gridcooling system being independent from control of the retarding grid. 16.The electric drive machine of claim 15, wherein the auxiliary driverincludes at least one of an auxiliary generator, a winding assembly anda bidirectional inverter enabling bidirectional electrical communicationbetween the generator and the DC bus.
 17. The electric drive machine ofclaim 15 further comprising one or more of a hybrid system, an energystorage device, a charging device, and a heating, ventilation andair-conditioning HVAC system coupled to the DC bus.
 18. The drive systemof claim 15, wherein the auxiliary driver includes at least one motorelectrically coupled to the auxiliary devices, the auxiliary drivertransmits electrical power to a DC bus during the trolley mode, theauxiliary devices are configured to draw electrical power from the DCbus during the dynamic braking mode and back drive the engine.
 19. Thedrive system of claim 18, wherein the auxiliary driver includes a DC/DCconverter enabling electrical communication between the trolley drivearrangement and the DC bus and power a DC motor through a contactor fromthe DC bus to power the generator and back drive the engine.
 20. Amethod for back driving an engine and allowing the supply of fuel to beshut off to the engine on an electric drive machine, the electric drivemachine having the engine coupled to a generator, a motor operativelycoupled to drive wheels, and auxiliary devices, the method comprisingthe steps of: providing an inverter circuit in electrical communicationbetween the generator and the motor; providing an auxiliary driver inelectro-mechanical communication between the generator and the auxiliarydevices; determining a current mode of operation of the electric drivemachine; automatically directing electrical power from the trolley drivearrangement to the motor in trolley propel mode through at least one ofthe inverter circuit and the auxiliary driver if the current mode ofoperation is in trolley mode; and automatically directingelectro-mechanical power from the motor to a one of the engine and thetrolley drive arrangement in a dynamic braking mode through at least oneof the inverter circuit and the auxiliary driver if the current mode ofoperation is in a dynamic braking mode.
 21. The method of claim 20,wherein the auxiliary driver includes at least one of an auxiliarygenerator, a winding assembly and a DC motor coupled to each of thegenerator and auxiliary devices.
 22. The method of claim 20, wherein theinverter circuit includes an inverter configured to automaticallycommunicate electrical power from the trolley drive arrangement to themotor so as to drive the drive wheels during the trolley mode, andautomatically communicate electrical power from the motor to a one ofthe generator and the trolley drive arrangement so as to transmit powerto the engine during the dynamic braking mode.
 23. The method of claim20, wherein the inverter circuit is electrically coupled to a retardinggrid and the auxiliary driver is in electrical communication with a gridcooling system, control of the grid cooling system being independentfrom control of the retarding grid.
 24. The method of claim 20 furthercomprising the step of automatically communicating power only betweenthe auxiliary devices and the engine via the generator if the currentmode of operation is in an idling mode.